The different images are memorized, after reception, in the electronic device 12 intended to restore them. At minimum, these different images are memorized in a “buffer” memory.
In the case of a specific IPTV stream, the considered memorization time is less than a second. In the other examples, the different components can be memorized in a hard disk type memory module, with a view to being decoded later, the applications associated with this memorization type are not then “real time” type applications.
In order to optimize the operation of the system, the receiver 12 must decode the packets 10 with a bitrate identical to the bitrate of their transmission. In fact, if the transmitter server 11 transmits the packets 10 with a bitrate greater than the decoding bitrate of the receiver 12, the buffer memory of the receiver is saturated by the quantity of packets 10 to be stored while waiting for their decoding. Conversely, if the transmitter transmits packets 10 with a bitrate less than the decoding bitrate of the receiver 12, the buffer memory of this latter remains waiting for data.
Consequently, the transmitter server 11 must transmit packets 10 synchronously with the processing carried out by the decoder 12. To enable this synchronization, it is known in the art to use a protocol known as TS (Transport Stream), that timestamps the information transmitted by means of indicators known as PCRs (Program Clock Reference).
Such a method has the advantage of enabling the transmission of a data stream with a bitrate that is practically constant, shown in FIG. 2. More specifically, the bitrate associated with packets 10 already described is shown in this FIG. 2 according to a time axis 18.
Hence, packet transmission 10 is assured if this fixed bitrate can be assured and maintained in the network during this transmission.
The present invention results from the observation that such a method can lead to restoration delays, also known as presentation, of a sample when its transmission is preceded by the transmission of a large sized sample.
For example, as shown in FIG. 1, a B′ image transmitted after an I′ image having required a long transmission delay can be received late for its restoration—the image restoration order, represented according to the axis 16, being reversible with respect to their transmission order in the MPEG protocol.
As a result, if the presentation of transmitted images takes place more rapidly than their transmission, particularly following the transmission of a large sized image, the decoder 12 ends by remaining in waiting for a B′ image for a delay period represented by the shaded area.